Field of the Invention
Many modern electronic devices use batteries to provide power. The use of batteries is advantageous because it allows the device to be used virtually anywhere. People have become accustomed to using devices which use rechargeable or easily disposable batteries. These devices include digital cameras, video recorders, lap top computers and cellular phones. For many of these devices, power consumption is generally not a problem. The device is simply turned on when needed, used, and shut off when finished. Thus, the battery is only drained when the device is actually being used.
For some devices, the operator may wish to use the device for an extended period of time, but only on an intermittent basis. For instance, when traveling in darkness in an outdoor environment, a person might use a night vision monocular scope to clearly view selected objects. During actual movement, however, the person may find it awkward to constantly look through the device. To use the device most efficiently, the person may cease movement, raise the device to their eye, look through it, and subsequently return it to a carrying position. Then the person would continue moving. While this may be an efficient way of using the device, it is not an efficient way of using the power supply because, the device is constantly using power, even while in the carrying position.
One simple solution would be to simply turn the device on and off. However, this can be clumsy and awkward, thus slowing the person down and detracting them from other tasks. Furthermore, many battery powered devices have relatively long power up and power down periods. More sophisticated devices might even have software applications which must be booted. All this renders it impractical to consistently be turning such devices manually on and off.
To solve this problem, some devices have incorporated a switch near the eye piece. When the operator looks through the device, their head contacts the eye piece thus causing the switch to turn the power on. In devices with long power-up times, the eye piece does not turn the device entirely on and off, but rather switches it from a low to high power state.
While providing a relatively simple and economical solution to the problem, the use of such a switch has many drawbacks. In order to be comfortably used, the switch must be relatively easy to engage. As such, many types of unintended contact will turn the device on and off. For instance, when carrying the monocular night vision scope in their hand, a person may bump the eye piece against their leg or other portion of their body thus inadvertently turning the device on. If such inadvertent contacts are frequent, there will not be any savings in power consumption from the incorporation of such a switch. An additional problem exists for users of such devices who wear eye glasses. The eye piece of the device must be pressed firmly up against the glasses, thus causing the glasses to press into the operator's head, which may cause pain or discomfort.
Another power reduction device is the use of an infrared sensor incorporated near the electronic device. The eye detector may detect heat from a person in close proximity or actually emit infrared beams and detect their reflection to determine when the device should be powered up. Simply detecting heat from a person is not always efficient because heat is generated by every portion of the body. Once again, causing the device to be powered up when it is not actually intended to be used, thus wasting power. Emitting infrared beams to detect the reflection causes two separate problems. First the emitter-detector uses a relatively high amount of power itself, thus negating many of the benefits intended to be derived. Second, such projected infrared beams can be detected by many extraneous sources, which is of particular concern when these devices are used in military operations.
With both the heat sensor and the emitter/detector combination, a problem exists for people who wear eye glasses as the lenses of the glasses may deflect infrared radiation thus preventing the detector from noting their presence and turning the device on.
Some electronic devices may use a complicated eye-imaging detector. Such a detector also suffers in that it uses a relatively large amount of power. In addition, the optics required to perform such imaging often increase the size of the device beyond what is commercially desired. Therefore, there exists a need to provide a simple and efficient proximity detector which brings the device from a low power usage state to a high power usage state.